DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 241631
SWODY1
SPC AC 241629

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1029 AM CST MON DEC 24 2012

VALID 241630Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVERNIGHT FOR PORTIONS
CENTRAL-E TX AND WRN LA...

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN WAS ANALYZED THIS MORNING OVER
CONUS...FEATURING TWO SHORTWAVE TROUGHS OF PRIMARY PERTINENCE TO
THIS FCST INITIALLY OVER...
1. MID-SOUTH REGION TO MS/AL COAST. THIS FEATURE WILL MOVE EWD AND
DEAMPLIFY SLIGHTLY BEFORE MOVING OFFSHORE SC AROUND 03Z.
2. INLAND PAC NW SSEWD ACROSS NV. PERTURBATION IS FCST TO
STRENGTHEN THROUGH PERIOD AND MOVE SEWD ACROSS CENTRAL/SRN
ROCKIES...REACHING CENTRAL/SRN HIGH PLAINS BY 12Z. EMBEDDED/500-MB
CLOSED LOW SHOULD FORM BY 12Z OVER TX PANHANDLE/SOUTH-PLAINS
REGION...WHILE MID-UPPER HEIGHT GRADIENT INTENSIFIES MARKEDLY TO ITS
SW-SE. BY 12Z...EXPECT 500-MB JET MAX 90-100 KT OVER SERN NM/TX
PERMIAN BASIN REGION...WITH FLOW STRENGTHENING TO 60-70 KT RANGE
OVER SFC WARM SECTOR IN SE TX.

AT SFC...WEAK LOW NOW OVER NRN KY IS FCST TO PROCEED NEWD UP OH
VALLEY THROUGH REMAINDER DAYLIGHT HOURS AND WEAKEN...WITH OCCLUSION
TRIPLE-POINT LOW POSSIBLY FORMING INVOF SERN NY COASTAL WATERS
AROUND 06Z. ACCOMPANYING SFC COLD FRONT WAS ANALYZED AT 15Z FROM
LOW SSWWD ACROSS NRN AL...SWRN MS...SWRN LA...AND S-CENTRAL TX. TX
PORTION OF BOUNDARY IS DECELERATING...AND IS FCST TO MOVE NWD ACROSS
PORTIONS CENTRAL/SE TX OVERNIGHT AS WARM FRONT. MEANWHILE...LEE
CYCLONE IS FCST TO DEEPEN CONSIDERABLY TODAY ACROSS NERN NM AND SERN
CO REGION...WITH APCH OF AMPLIFYING TROUGH ALOFT. DURING LAST 6
HOURS OF PERIOD...SFC CYCLONE WILL TRANSITION TO FRONTAL-WAVE
FEATURE AND MOVE/REPOSITION SEWD ALONG ZONE OF
FRONTOGENESIS...REACHING POSITION OVER CENTRAL TX BY 12Z.

...TX/LA AREA OVERNIGHT...
CONVECTIVE POTENTIAL WILL INCREASE OVERNIGHT...FIRST N OF SFC FRONT
LATE EVENING THROUGH PRE-DAWN HOURS WITH MOST INTENSE CELLS POSING
HAIL THREAT. ACTIVITY MAY DEVELOP PROGRESSIVELY CLOSER TO FRONT
THROUGH END OF PERIOD...EVENTUALLY BECOMING SFC-BASED WITH
SUPERCELLS AND BOW/LEWP FEATURES POSSIBLE. AS SUCH...THREAT EXISTS
DURING LAST FEW HOURS OF PERIOD FOR SVR HAIL/GUSTS. TORNADO RISK
EXISTS FROM ANY SFC-BASED AND RELATIVELY DISCRETE CELLS IN WHAT
SHOULD BE VERY FAVORABLE SHEAR ENVIRONMENT...BUT COVERAGE OF
SFC-BASED TSTMS IS TOO UNCERTAIN ATTM FOR MORE THAN 5% UNCONDITIONAL
TORNADO RISK.

DEEP SHEAR AND LOW-LEVEL HODOGRAPHS EACH ARE EXPECTED TO STRENGTHEN
OVER RETURNING WARM SECTOR TONIGHT...AS 60S F SFC DEW POINTS
CONTRIBUTE TO 1000-1500 J/KG MLCAPE BY 12Z ALONG AND S OF FRONT OVER
SE TX. LARGEST LOW-LEVEL HODOGRAPHS WILL BE ALONG FRONT...WHERE
BACKED SFC WINDS WILL CONTRIBUTE TO EFFECTIVE SRH 300-500 J/KG. SRH
ALSO WILL BE FAVORABLE FARTHER S OVER COASTAL AREAS IN WARM
SECTOR...HOWEVER FCST SOUNDINGS SUGGEST PRONOUNCED EML-BASE
INVERSION BETWEEN 850-700 MB THAT MAY RESTRICT TSTM COVERAGE AWAY
FROM BOUNDARIES.

...CENTRAL-ERN GULF COASTAL PLAIN...NEXT 4-6 HOURS...
BULK OF CONVECTION IS EXPECTED TO OUTRUN LOW-LEVEL DESTABILIZATION
OVER THIS REGION THROUGH REMAINDER DAYLIGHT HOURS. HOWEVER...AT
LEAST ISOLATED TSTMS STILL MAY DEVELOP OVER THIS AREA THROUGH AROUND
21Z...SOME OF WHICH MAY BECOME SFC-BASED. DAMAGING WIND AND TORNADO
RISKS ARE NONZERO BUT VERY CONDITIONAL. DESTABILIZATION WILL BE
SLOWED BY ONGOING CLOUDS/PRECIP...WHICH WILL RESTRICT PACE OF
DIURNAL WARMING. LOW-LEVEL THETAE ADVECTION SHOULD RESULT IN
POTENTIAL INFLOW PARCELS EFFECTIVELY BECOMING SFC-BASED ACROSS THIS
REGION THROUGH MID-AFTN...WHILE DEEP-LAYER ASCENT WEAKENS. THESE
OFFSETTING INFLUENCES WILL AFFECT TSTM COVERAGE...BUT ANY
SUSTAINED/SFC-BASED CONVECTION HAS POTENTIAL TO BECOME
SUPERCELLULAR. AS SUCH...WILL MAINTAIN MRGL UNCONDITIONAL SVR
PROBABILITIES FOR THIS OUTLOOK.

..EDWARDS/COHEN.. 12/24/2012

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